ABOVE: Don't look down--instead, check the local floodwater level with the Venice tides app for iPhone.

Acqua alta, or tidal flooding, is an increasingly frequent annoyance in Venice from late October through early spring. (We cover the phenomenon--and how to prepare for it--in an illustrated article at Veniceforvisitors.com.)

Fortunately, the local government authorities offer plenty of advance warning via a Web site and alarm sirens most of the time, making it relatively easy to avoid low-lying areas that are likely to get covered with water when an unusually high tide pours into the Venetian Lagoon. But if you've got an iPhone, iPad, or iPod Touch, there's an even better way to keep your Ferragamo pumps from turning into sponges: Buy the "Venice tides" mobile app, which is available from Apple's iTunes.

Venice tides isn't the only acqua alta app on the market, but it has a big advantage over its competitors: Its interface is simple, uncluttered, and easy to understand even if you've never waded through tidal charts.

The main screen (photo on right) shows a building, a fondamenta (canalside sidewalk), and the water of a canal. As the acqua alta rises, so does the water on your iPhone's screen. The app also shows the current height of the tide in centimeters, compared to the street level. You can also see how high the anticipated peak tide will be and when it will occur, so you'll know if you have time to reach a local destination or get back to your hotel.

If you're curious to know what the next couple of days will bring, just turn your phone sideways. A new screen will appear, showing expected high and low tides (including times and levels in centimeters) over the next two days.

Venice tides has other features, too. You can customize the app street level to match your location within the city, and you can ask the app to send you a notification (a.k.a. a warning) before the next acqua alta occurs.

We've tried the Venice tides app, and we like it. If you plan to be in Venice for a couple of days or longer during the acqua alta season, or if you want to know whether the streets will be wet when you arrive, Venice tides is likely to be a useful tool. For more information, go to:

www.pugosoft.com/en/apps/venice-tides

(Note: The full Venice tides app is inexpensive, but there's also a free "Venice tides lite" version that includes all features except for push notifications.)

BELOW: Turn your iPhone, iPad, or iPod sideways to see a two-day tidal chart:

Photo and screen shots: Mattia Fort and Valentina Venza, Pugosoft.

In terms of elevation, the Piazza San Marco is one of Venice's lowest points: The Piazza is almost at the same level as the Venetian Lagoon.

Storm sewers in the Piazza empty into St. Mark's Basin (near the entrance to the Grand Canal), and during high tides, it isn't unusual for water to back up through the drains and into the square.

Such flooding is most dramatic during acqua alta (flood tides that occur mostly from October through April), but it can happen at any time of year--even on warm spring and summer days, when children and tourists are fascinated by puddles on the Piazza:

The city of Venice and software developer Diego Pizzocaro have announced a free smartphone app titled "hi!tide Venice." The app is available in English for both iOS (iPhone) and Android, and it predicts acqua alta (tidal flooding) with data supplied by Venice's official tidal-monitoring and flood-warning service, the Istituzione Centro Previsioni e Segnalazioni Maree.

The app's main screen shows the current tide plus anticipated low and high tides over the next two days. You can click on a daily forecast for a more detailed view that includes an hour-by-hour graph.

You'll also see icons for "Places" and "Ferries" that show current tide levels at main points of interest (such as the Piazza San Marco) and vaporetto piers.

To download the free app from Apple's App Store or the Android Market, click the links on:

City of Venice: Tide Forecast Apps